This invention relates to a method of forming a tubular member in general, and specifically to a method of simultaneously forming a tubular member with a flange.
Hydroformed tubular members used as structural components in a vehicle body frame or subframe often have to be structurally joined at some point along their length to other vehicle body members. Therefore, it is useful if the tubular member as formed can be given a localized attachment flange, of the proper shape and size, that is formed as part of the basic hydroforming process, without having to be welded on after the fact.
U.S. Pat. No. 5,070,717 to Boyd et al, co assigned, shows such a process. As disclosed, the dies that close around the cylindrical tubular blank before it is internally pressurized have a pair of spaced shoulders that pinch off and flatten a portion of the tube. This creates a closed, double thickness flange on the side of the fully formed tube that is a continuation of the closed interior of the tube. The flange so formed cannot be made particularly wide, nor with a complex, open shape. A flange so limited can be used in some applications, however, and the great advantage of the method is that it involves essentially no process steps beyond the basic forming process itself.
In applications where a wider and complex, open shaped flange is needed, it is simply stamped out separately and welded on as a final step. It would be an economic advantage to incorporate at least some of the processing of such a flange into the hydroforming process, as well.